The present invention relates to a method for finding the existence or nonexistence of disconnection (breaking) of conductive wires in antifogging glass or antenna glass used in vehicular windows and the like.
A conductive paste is printed on a plate glass by screen printing or the like to form conductive wires thereon. In vehicular plate glass, such conductive wires are used for heating plate glass by applying electricity to the conductive wires to provide antifogging property and are used as an antenna for telecommunication. These functions of conductive wires may be impaired by disconnection of the conductive wires. Therefore, it is necessary before shipping to inspect conductive wires to see if they have disconnection or not.
Japanese Patent Application Publication No. 6-249905 discloses a method for finding disconnection of conductive wires in an antifogging glass. In this method, electromagnetic energy generated by applying a voltage to the conductive wires is detected by a detecting head. Furthermore, a conductive wire position detecting sensor is provided for outputting a detection signal when the detecting head is above the conductive wires. The detecting head, together with the sensor, is moved along the surface of the antifogging glass. The output signals from the detecting head and the sensor are input into a computer to judge whether or not there is disconnection.
Hitherto, finding disconnection of conductive wires has been conducted by moving a sensor along the surface of antifogging glasses in the mass production of antifogging glasses, as disclosed in Japanese Patent Application Publication No. 6-249905. However, the productivity is not so good, since it is necessary to change the manner of moving the sensor for a different type of antifogging glass. Furthermore, it may be difficult to distinguish a first conductive wire having disconnection from a second conductive wire having no disconnection, if the first and second conductive wires are close to each other. Still furthermore, the movement and the position of the sensor may be limited in the case of an antifogging glass having a small curvature (steep curve). With this, the accuracy for finding disconnection may be lowered.